Levels of chlorinated hydrocarbons and composition of PCB in herring gull Larus argentatus eggs collected in Norway in 1969 compared to 1979–1981

Eggs from herring gull Larus argentatus were collected at seven different locations along the Norwegian coast in 1969 and again in 1979–1981. Hexachlorobenzene (HCB), octachlorostyrene (OCS), DDE, PCB and decachlorobiphenyl (DCB) were determined in each of the 200 eggs. In order to obtain additional information on the time trend of the PCB levels, the relative distribution of four selected PCB components was determined to see if there had been a shift towards the more persistent PCB isomers. Such a shift may indicate a decreasing tendency in PCB levels. Mean levels of HCB in 1969 and 1979–1981 were 0·19 and 0·12 μg g⁻¹ wet weight, respectively. When excluding the results from Telemark, an area with local contamination with HCB, OCS and DCB, there were no statistical differences in HCB levels between the two sampling periods. OCS and DCB were only detected in eggs from Telemark. Significant decreases in DDE levels and DDE/PCB ratios but not in PCB levels were observed between 1969 and 1979–1981. Only for the most persistent of the PCB isomers recorded was there a small increase in the relative amount from 1969 to 1979–1981.